I have never gotten an upgrade at check-in. I've come to think that it's a meaningless option.

I am also wary that something is up with the AU process. I'm on a flight first thing this coming monday morning, FLL-EWR. The inventory was showing A9 a couple of days ago, and today is showing A0. I know CO can sell F in this market up until last minute, so they don't always run AU at the five day point, and sometimes not until a few hours ahead. They also sometimes don't run AU until the last minute as they hold seats to rebook cancelled and severely delayed flights from the night before. However, it seems like AU ran at the 3 day mark in this case, and all those empty seats disappeared. I'm at a lower (but not the lowest) fare class, but even so, I was surprised to left be left behind as a plat with that many empty seats. Following the examples of others, above, I called the elite line, and got a rather lazy sounding agent who claimed that all those seats went to mileage upgraders, and AU never ran as a result.

I'm suspicious.